DHAKA, Bangladesh – Explosions of homemade bombs were reported across the Bangladeshi capital Tuesday as opposition activists enforcing a daylong general strike rioted and clashed with police.

Police fired tear gas to disperse crowds of people who were smashing vehicles. It was not immediately clear if anyone was injured in the violence described by witnesses and television reports in parts of the capital, Dhaka,

A coalition of 18 opposition parties was enforcing the strike to demand that a caretaker government be restored before the next national elections due in 2014, while a key coalition partner wants their leaders facing charges of crimes against humanity be freed from jail.

Schools and businesses remained closed in Dhaka and other major cities and towns Tuesday and transportation was largely disrupted across Bangladesh, a parliamentary democracy that has a history of fierce political violence.

Amid the violence, the United States on Tuesday urged the two main political parties to resolve their disputes through dialogue.

Independent television reported detention of at least six opposition activists from Dhaka University area in the capital.

Police said activists torched at least 21 vehicles in Dhaka late Monday after police arrested a senior leader of the main opposition Bangladesh Nationalist Party, led by former Prime Minister Khaleda Zia.

Jamaat-e-Islami, the country's largest Islamic party and the main partner of Zia's party, has been demanding the release of nine of its leaders facing charges of crimes against humanity dating back to the 1971 independence war against Pakistan. Two other leaders from Zia's party face similar charges and are now jailed.

Zia criticized the trial, calling it a farce.

In 1971, Bangladesh — at the time, the eastern wing of Pakistan — became independent after a bloody, nine-month war with the help of India, Pakistan's bitter rival.

Jamaat-e-Islami leaders are accused of aiding the Pakistani army in killing and raping during the war. The leaders are behind bars pending trial proceedings. But Jamaat-e-Islami says the charges are politically-motivated.

Police said Mirza Fakhrul Islam Alamgir, acting secretary general of Zia's party, was arrested Monday on charges of instigating violence and torching a vehicle during a nationwide road blockade on Sunday.

Dozens of vehicles were burned and smashed Sunday and at least two people died during the opposition-sponsored blockade.

The government of Prime Minister Sheikh Hasina scrapped the 15-year-old caretaker system last year in line with a Supreme Court order that ruled it unconstitutional, saying the constitution allows only popularly elected people to run the government. Opposition parties fear the election will be rigged if the current party remains in power.

The government has blamed the opposition for the recent violence, saying the protests are aimed at protecting 1971 suspects. The administration has vowed not to go back to the unconstitutional provision of the caretaker government system.

Hasina's Awami League party and Zia's Bangladesh Nationalist Party are the main contenders for securing power.

Robert O. Blake, U.S. assistant secretary of state for South and Central Asian Affairs, called upon the bickering parties to hold a dialogue to find a solution to the political impasse.

Blake, who was on a four-day official visit to Dhaka, told reporters at a press conference that the U.S. would support any resolution that would come from the two major parties.